Describe the rooms, not just the area
A bedroom and a new kitchen add different services and finishes, even if they have the same floor area. Write down each room's purpose, storage needs, fixtures and connections to adjoining spaces.
Use our home renovation planning guide to separate must-haves from optional improvements. For house extensions in Wellington, an early brief should also explain why the current home no longer works for your household.
Include the existing-house connection
Budget discussions often focus on the addition itself. Also list the walls, floors, roof areas and services affected where it meets the house. Include finishing work in rooms that remain and any temporary protection needed while the connection is open.
For example, an added living room may require work to an existing kitchen wall and floor. Treat those as named parts of the scope, rather than assuming the extension price covers everything nearby.
Home extension costs in NZ: a whole-project budget
| Budget area | Questions for your brief |
|---|---|
| Design and approvals | Which drawings, investigations and specialist inputs are needed? Who arranges them? |
| Site preparation | What access, ground work, protection and removal are involved? |
| New construction | What structure, envelope, services and finishes are included? |
| Existing house | Which junctions, rooms and finishes need alteration or making good? |
| Household costs | Will accommodation, storage or temporary facilities be needed? |
Identify what still needs investigation
Ground conditions, existing construction and access can affect the work. Ask which assumptions the estimate relies on and what information would make them more certain. Keep an uncertainty register with the issue, the person checking it and the point when an answer is needed.
Where a quote includes an allowance, use the provisional sum guide to understand what is covered and how the final amount will be determined. Keep your contingency separate from optional finish upgrades.
Compare the same project
Give each quote the same drawings, selections and inclusion list. Check whether the prices include GST, design work, approvals, site arrangements and completion of the surrounding rooms. A square-metre comparison alone can conceal those differences.
Send us the rooms you need, your plans and the existing-house changes you expect. We can discuss your extension scope and the information needed for a useful construction quote.